Submission #1008067

#	Time	Username	Problem	Language	Result	Execution time	Memory
1008067		andecaandeci	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	45 ms	7896 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

typedef long long ll;
const ll INF = 1e9;
const ll MOD = 1e9 + 7;
const ll MAXN = 2e5 + 5;
const ll LOG = 31;
#define vll vector <ll>
#define pll pair <ll, ll>
#define fi first
#define se second
#define endl '\n'

ll n, m;
ll a [MAXN], b [MAXN], pf [MAXN];
vll v;

// V(x, y) = dep[x] + dep[y] - 2*dep[lca]
// cari V(x, y) terkecil ke (1 - 10^5)

ll sum(ll x, ll y){return ((x%MOD)+(y%MOD))%MOD;}
ll sub(ll x, ll y){return ((x%MOD)-(y%MOD) + 2*MOD) % MOD;}
ll mul(ll x, ll y){return ((x%MOD)*(y%MOD))%MOD;}
ll pwr(ll x, ll y){
    if(y == 0) return 1;
    ll ret = pwr(x, y/2);
    ret = mul(ret, ret);
    return (y & 1) ? mul(ret, x) : ret;
}
ll dvi(ll x, ll y){return mul(x, pwr(y, MOD-2));}

ll f(ll x){return dvi(mul(x, x+1), 2);}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin >> n;
    for(ll i = 1; i <= n; i++) cin >> a[i];
    for(ll i = 1; i <= n; i++){
        cin >> b[i];
        pf[i] = pf[i-1] + b[i];
    }
    ll ans = 0;
    for(ll i = 1; i <= n+1; i++){
        while(!v.empty()){
            if(a[v.back()] < a[i]) break;
            ll h = a[v.back()], tes = a[i];
            ll w = pf[i-1];
            if(v.size() >= 2){
                tes = max(tes, a[v.end()[-2]]);
                w -= pf[v.end()[-2]];
            }
            // cout << h << "," << tes << " " << w << " << " << mul(sub(f(h), f(tes)), f(w)) << endl;
            ans = sum(ans, mul(sub(f(h), f(tes)), f(w)));
            v.pop_back();
        }
        v.push_back(i);
    }
    cout << ans << endl;
}

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 18 / 18
• Subtask 7: 27 / 27